This invention relates to sliding armature braking motors in general and more particularly to an improved arrangement for increasing the axial force in such a motor. Sliding armature braking motors in which the rotor of the motor is biased by a spring or other means to cause a brake disc to be held against a braking surface and which rotor when energized develops forces to move the brake disc away from the braking surface are known in the art. One such arrangement is described in German Auglegeschrift No. 1,037,570 in which a motor with a conical rotor is provided. When the end face of the lamination stack is near the air gap, an iron body, by which part of stator stayed flux is deflected from its normal path leading transversely to the heads of the teeth in the slots, conducts a portion of the flux. In another known design, the spring acting in the axial direction is further designed as a torque spring and held with its one end at the shaft of the drive motor and its other end at the brake disc and is guided on the shaft rotatably and movable length wise. Through this arrangement the braking motor need not start up immediately after it is switched on, but enters into a phase of power transmission between the shaft and braking disc through the then tensioned torsion spring. Only when the slip is small and after it has reached its maximum torque does it develop a large electromagnetic force for lifting the brake disc.
Designs such as this which have a large number of moving parts are relatively expensive and trouble prone. In order to get along without these moving parts the axial braking pressure must be reduced which results in an undesirable expansion of the runout time during braking. Another solution is to make the braking motor larger for the same required braking power.
Thus, it can be seen that there is a need for a braking motor of this nature having a simple design and which provides the high braking forces required.